Method of producing titanium



1960 J. 1.. VAUGHAN 2,936,232

METHOD QF PRODUCING TITANIUM Filed D60. 31, 1954 TiCl 4 *l 28 Reducing Agen'l' QJj ?1 To Vacuum Pump To Vacuum Pump My? FIG. I

A INVENTOR. JR he; V407 kaa BWQJ. M70

ATTORNEY Unite Sta es This invention relates-to the'production of metals and more particularly to the production of refractory metals ,such as titanium and the like.

A principal object of the present invention is to provide an improved apparatus and process for the production of titanium and like metals by the multi-stag'e reduction of a like metal compound halide bath. v

Another object of the invention is to provide an improved apparatus and process of the above typewhich is particularly adapted to large-scale commercial oper ation with high rates of production.

Still another object of the invention is to provide contained in amojlten an improved process and apparatus of the type generally described in the copending application of Hnilicka, Serial No. 461,981, filed October 13, 1954, now Patent No.

" 2,347,205, granted August 12, 1958.

ater ridding contaminants, but it is permissible tofprovide for other means which will provide an inert atmosphere. The first stage reactor is further provided with means for introducing titanium tetrachloride below the surface of the molten halide bath where an agitator means is located to provide intimate contact between the titanium tetrachloride and the lower chlorides of titanium, pref= erably the dichloride, contained in the" bath. The reac= tion which results may be represented as:

The agitator means is further adapted to circulate the bath so that the TiCl product is made available to react'with a reducing agent which is fed into thehalidebath at a'point or Zone spaced apart from the point or zone where titanium tetrachloride is introduced. The 7 rate at-which circulation is carried out is that which preferably produces an amount of lower chloride of titanium per cycle which is less than 1 weight percent of the amount of bath being circulated. The reducing agent is preferably sodium but may be one or more metals from 1 '1 the class consisting of lithium, sodium, potassium, mag- Qther objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the apparatus possessingthe construction, combination of elements and arrangement of parts, and the process involving the several steps and the order lsof one or more of'such steps with respect to each f the others, which are exemplified in th e'followingdet ailed disclosure and the scope of the application-of which, will be indicated in the claims; I

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detaileddescription taken in' connection with the accompanying drawings wherein:

Fig. 1 is;a diagrammatic, schematic drawing illustrat .ing one preferred embodiment of theinvention; and

Fig. 2 is a diagrammatic, enlarged --detail of another portion of Fig. 1.

The production of titanium and related metals is accompanied by many difficulties. v It is the intention of the present invention to provide an improved apparatus and process providing for multi-stage reduction} of a In an earlierstage reactor, it is' intended 'thattitanium tetrachloride be partially reduced by a reducing agent to lower chlorides while contained ina molten halide bath. "Transfer means are provided ,which carry the' -realcted bath in an uncontaminated state from" the earlier stage reactor to a separate later stage. reactor for further reduction of thetitanium lower *ChlO titanium compound.

rides to metallic titanium. g

In order to achieve'the objects set forth, the earlier stage reactor, which for convenience will be referred to hereinafter as the first stage reactor, is designed to accomplish the reduction of titanium tetrachloride to lower chlorides in the follewing manner. The first stage reactor is :j-adapted to form a chamber within which to 1 locate a molten halide bath containing lower chlorides of titanium. The molten halidebath, is preferably sodium chloride. but may be one or more of the halides of the class consisting of alkali metal halides and alkaline earth I inet al halides. E vacuationf'means, are. proyided for 'nesium and calcium. It is preferred that the amount of reducing agent used bestoichiometrically less than that required to reduce the total titanium halide content within I the bath'below titanium dihalide. In this manner a preferred average titanium valence of 2.2 is maintained; At the same time, the preferred mole ratio of sodium to titanium tetrachloride feed is maintained at less than.

1.8 to 1.0. In this manner-"a desired which may be represented as 2TiCl +2Na- ZNaCH-ZTiCl overall reaction is substantially achieved. However, some titanium, di-

chloride and trichloride will contact the sodium soft hat titanium fines are also produced in a manner represented as: if V F TiCl +2Na 2NaCl+Ti In order "to digest the fines, which at this stage are undesirable, to a soluble lower chloride, more preferably the dichloride, the bath is allowed a residencetime on the order of two hours. in situ before transferring it through transfer means to the later stage reactor'for' further reduction of the lower chlorides to metallic titanium. The digestion reaction may be represented as:

The preferred transfer means is' arranged" to facilitate an uncontaminated transfer of the molten halide bath and is further provided with means for forming a frozen salt plug capable .of sealing off the first stage'reactor.

Within the second stage reactor, of which there may be more than one to increase production, a reducing agent, again preferably sodium, is introduced to the sur face of the molten salt bath and reacts with the lower chlorides contained in the molten halide, bath to form- 4 metallic titanium. This reaction maybe represented as:

' rich-tam ZNaCH-Ti I The second stage reactor is also preferably provided-with baffle means with which to encourage growth of metallic titanium in crystalline form 1 by restricting. and rninimizing convection current activity. Preferably the bafilermeans will be in the form of a removable 'lattice structure of horizontal convection current baffles.

Referring now to the drawings, shown inFig. 1 is; one

preferred arrangement of elements embodied in'the pres ent invention. The earlier or first stage reactor is shown at, 10, available to feed a later or second stagetreactor 12 through a transfer means, Thefirst stage reactor 10,

V z', 936,;232 Patented May 9' v which is adapted to be evacuated through means 11, comprises a chamber 16 within which is achieved partial reduction of titanium tetrachloride to a solution of lower chlorides in a molten halide bath. Located to the outside of first stage reactor 10, and extending down part way on the transfer means 14, is a means 38 for removing excess heat from the molten halide bath and also for supplying heat when desired. In producing the desired partial reduction, titanium tetrachloride is preferably 'introduced below the surface of the molten halide bath by means 20 which is preferably a tube. The molten halide bath 18 is preferably a halide or eutectic mixture of halides chosen from the class consisting of alkali metal halides and alkaline earth metal halides. In one preferred embodiment, sodium chloride is used. The titanium tetrachloride introduced to the bath, and represented after its introduction by bubbles 22, is brought into intimate contact with the lower chlorides of titanium, preferably the dichloride, in a first zone through the action of agitator means 24 to form titanium trichloride. Agitator means 2 issuspended in the molten halide bath 18 by a' shaft 26 which is in turn driven by a motor 28. Agitator means 24 is preferably a turbine and is adapted to circulate the titanium trichloride which is formed in a first zone to a second zone preferably located at the surface of bath 18. The reducing agent is preferably intro duced into chamber 16 by a means 30 which comprises a pipe and is uniformly distributed to the surface of inolten bath 18 through the agency of spinning disc 32. As a result of so contacting the reducing agent, preferably sodium, with titanium trichloride and titanium dichloride, additional lower chlorides are formed in the molten halide bath 18 along with titanium fines. The molten halide bath 1% is retained in situ until such time as the titanium fines have been digested again to lower chlorides of titanium, which will preferably go into solution with the said molten halide bath.

The transfer means 14 preferably comprises a rigidly positioned pipe member 36, one end of which penetrates the bottom of the first stage reactor 10', extending up from the bottom of the reactor 10 to a height slightly above that a which the agitator means 24 is suspended. Transfer means 14- is provided with means for forming a frozen salt plug represented at 4!} which preferably comprises a trap means 42 and freezing coils 44. The trap means 42 is illustrated as including a sump 43 for collecting a charge of molten salt which can be frozen by coils 44 to plug the end of pipe 36. Additional molten salt flowing down pipe 36 after freezing of the bottom plug will also be frozen, at least near the bottom of pipe 36. The lower end of trap means 42 extends into sealing means 46, the lower end of said sealing means 46 being adapted to form a vacuum seal 48 with a corresponding seal means 54 of the second stage reactor 12. Sealing means 46 is provided with means 50 and 52 for evacuating and/or flushing said sealing means with an inert gas such as argon. In order to protect the sealing qualities of vacuum seal 48, which would be adversely aifected by heat given off from the molten halide bath during transfer, the walls of sealing means 46 are preferably of light construction and comprise a material having relatively low heat conductance, thereby forming an effective heat break.

For the sake of clarity, Fig. 2 is provided to show the details of vacuum seal 48. The second stage sealing means 54 is provided with a channeled fiange 58. the channel 60 of which is adapted to contain a meltable metal sealing material 62, into which material the lower end of sealing means 46 is adapted to be inserted after sealing material 62 (e.g., solder or the like) has been melted by a suitable heater (not shown). When the seal is in position, the solder 62 is again frozen to complete the seal.

Returning now to Fig. 1, seal means 54 is preferably a hollow extension of the second stage reactor 12 which 'is' provided with vacuum closure 64 adapted to be opened through manipulation of sliding door 66. This arrangement facilitates evacuating or, if preferred, purging of chamber 70 with inert gas prior to positioning reactor 12 to receive the molten halide bath, transferred from the first stage reactor 10.

Second stage reactor chamber 70 is adapted to be evacuated through the pipe means 68. Located within the chamber 70 are baffle means 72 adapted to restrict convection current activity within molten halide bath 80. Preferably the bafiie means 72 is constructed so as to form a removable lattice structure, the horizontal convection current bafiles 72 thereof being supported by support 74 located within chamber 70. It is also preferred that the removable lattice support '74 be provided with a perforated horizontal member 76 located above the horizontal convection current baflles 72 and adapted to support an initially formed metallic titanium crust. The second stage reactor 12 is further provided with means 84 for introducing a reducing agent, preferably sodium, to the surface of the molten halide bath 80. This introducing means 84 is preferably in the form of a spinning disc which is supported by shaft 86- driven by electric motor means 88. A pipe 99 is provided for supplying the reducing agent from an outside source (not shown) to spinning disc 84. A positioning means 100, one preferred embodiment of which is a hydraulic lift, is utilized to properly align and contact the second stage reactor 12 with transfer means 14, thereby insuring that vacuum seal 48 is secured and that a vacuum-tight passage is had for transfer of the molten halide bath from first stage reactor 10 to second stage reactor 12. In order to expedite transfer of the molten halides from the first stage reactor 10 to the second stage reactor 12, pressure-equalizing pipe 92 is provided, to be opened or closed by valve 94.

Growth of titanium crystals will start on the perforated horizontal member 76 and then on the remaining parts of the baffle means 72 which are in contact with the molten halide bath 80. This is facilitated by locating the perforated horizontal member 76 at a point or zone conveniently near wheresodium enters the bath 80. Metallic titanium deposits on a given structure in the form of an accretion which is'initially fines, later followed by the growth of large crystals. In order to aid in the deposition of the titanium and, more particularly, to facilitate growth of large crystals of titanium, convection currents, which result from heating or cooling of bath 30, are localized and minimized by the use of the bafile means 72. The entire structure 74 is constructed so as to be removed from chamber 70 for removal therefrom of the metallic titanium product 82 and for any further processing which may be desired.

In the operation of the complete equipment illustrated in Figs. 1 and 2, first stage reactor chamber 16 and pipe member 36 are evacuated and/or purged by an inert gas such as argon. A charge of molten anhydrous metal halide containing titanium dichloride, sufficient to fill pipe means 36 and reactor chamber 16 to a point above the top of pipe 16, is then preferably poured into the reactor. Cooling coils 44 are then operated to freeze a portion of the molten salt mixture and form the salt plug 46. Titanium tetrachloride is then pumped in through tube 20 to enter below the surface of the molten halide bath. Agitator means 24 is then put into operation and thereafter reducing agent, preferably sodium, in an amount previously described is preferably entered into the chamber 16 through pipe 30 and distributed to the surface of the bath. Residence time requirements are satisfied and, as a result, the produced lower chlorides of titanium are dissolved in the molten salt bath.

A second stage reactor 12, the reaction chamber 70 of which has been evacuated and provided with baffle means 72, is aligned and positioned to form a vacuum seal at 48 with transfer means 14. The now enclosed spacein pure metal.

the transfer means '14 which is located between the salt plug 40 and vacuum closure 64 is evacuated and purged with argon. Sliding door 66 is opened and operation of the cooling coil 44 is discontinued to allow the salt plug to melt. Vacuum break line 92. having been attached, valve 94 is opened and the molten halide bath passes through the transfer means 14 and into the second stage reactor chamber 70. After transfer of the molten halide bath is completed, the sliding door 66 and valve 94 are vclosed, and the second stage reactor may be relocated elsewhere'or left in situ to further reduce the dissolved lower chlorides of titanium to metallic titanium. In

.either case, the first stage reactor is again ready tolbe operated. The second stage reactor chamber 70 is filled by the transferred molten halide bath to a height above that at which the horizontal perforated member 76 is positioned. Sodium distribution means 84 is then operated and sodium is distributed to the surface of the bath 80, producing metallic titanium 82.

The apparatus described above is preferably made of Inconel or nickel so as to resist the corrosive action of titanium chlorides and sodium chloride or other halides used.

The present invention may, in addition to being used in the production of metallic titanium, be employed for the manufacture of other refractory metals by reduction of suitable compounds carried in a fused salt; It can also be used to coreduce several metallic compounds to form alloys thereof. Accordingly, when the expressions titanium or metal and the like are used in the appended claims, they are intended to include alloys as well as the Since certain changes may be made in the above process and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description, and shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: t 1. In a multi-stage process for the production of metallic titanium from dissolved titanium chlorides contained in a molten halide bath comprising sodium chloride, the

steps of feeding titanium tetrachloride to thebath'below the surface thereof, agitating the bath to provide intimate contact between the titanium tetrachloride and dissolved titanium dichloride, feeding sodium to the surface of the bath in an amount stoichiometrically'less than that required to reduce the total titanium chloride content Within the bath below titanium dichloride, the feed of sodium resulting in the production of a mixture of titanium fines, titanium dichloride and titanium' trichloride, digesting said titanium fines in the bath totitanium dichloride by reaction with dissolved titanium trichloride over an extended period of time to provide a bath whose titanium content is essentially in the form of dissolved titanium dichlorideand dissolved titanium trichloride, and

thereafter transferring the bath containing said titanium chlorides to a second stage for further reduction to metallic titanium, the average titanium valence being maintained above 2.0 during substantially all the extended period of time, the fused bath at the time of transfer having an average titanium valence on the orderof 2.2.

2. The process of claim 1 wherein the reduction of titanium dichloride to metallic titanium is carried out in the second stage by introducing a reducing agent to the transferred bath while restricting convection current activity within said transferred bath.

References Cited in the file of'this patent 1 UNITED STATES PATENTS 

1. IN A MULTI-STAGE PROCESS FOR THE PRODUCTION OF METALLIC TITANIUM FROM DISSOLVED TITANIUM CHLORIDES CONTAINED IN A MOLTEN HALIDE BATH COMPRISING SODIUM CHLORIDE, THE STEPS OF FEEDING TITANIUM TETRACHLORIDE TO THE BATH BELOW THE SURFACE THEREOF, AGITATING THE BATH TO PROVIDE INTIMATE CONTACT BETWEEN THE TITANIUM TETRACHLORIDE AND DISSOLVED TITANIUM DICHLORIDE, FEEDING SODIUM TO THE SURFACE OF THE BATH IN AN AMOUNT STOICHIOMETRICALLY LESS THAN THAT REQUIRED TO REDUCE THE TOTAL TITANIUM CHLORIDE CONTENT WITHIN THE BATH BELOW TITANIUM DICHLORIDE, THE FEED OF SODIUM, RESULTING IN THE PRODUCTION OF A MIXTURE OF TITANIUM FINES, TITANIUM DICHLORIDE AND TITANIUM TRICHLORIDE, DIGESTING SAID TITANIUM FINES IN THE BATH TO TITANIUM DICHLORIDE BY REACTION WITH DISSOLVED TITANIUM TRICHLORIDE OVER AN EXTENDED PERIOD OF TIME TO PROVIDE A BATH WHOSE TITANIUM CONTENT IS ESSENTIALLY IN THE FORM OF DISSOLVED TITANIUM DICHLORIDE AND DISSOLVED TITANIUM TRICHLORIDE, AND THEREAFTER TRANSFERRING THE BATH CONTAINING SAID TITANIUM CHLORIDES TO A SECOND STAGE FOR FURTHER REDUCTION TO METALLIC TITANIUM, THE AVERAGE TITANIUM VALENCE BEING MAINTAINE ABOVE 2.0 DURING SUBSTANTIALLY ALL THE EXTENDED PE- 